Abstract

PURPOSE: Shock wave lithotripsy (SWL) induces acute kidney injury (AKI) that extends from the papilla to the outer cortex by causing ischemia and the production of nephrotoxic agents. Direct ischemic damage and the generation of free radicals cause injury to the proximal tubular cells. Kidney Injury Molecule-1 (KIM-1) is a transmembrane glycoprotein that is upregulated in proximal tubular cells following ischemic or nephrotoxic injury and is not expressed in healthy kidneys. We evaluated the extent of free radical production in response to SWL by measuring urinary total antioxidant capacity (TAC) and total oxidant status(TOS). Furthermore, we investigated the severity of SWL induced kidney injury by measuring KIM-1 expression levels.

MATERIALS AND METHODS: The study population was comprised of 30 patients that were carefully selected and 30 age and gender matched control subjects. All patients received the same SWL procedure. Midstream urine samples were collected from patients before SWL and at 120 minutes following SWL. Urine KIM-1 levels were measured by ELISA, and TAC and TOS were measured via spectrophotometry.

RESULTS: Mean levels of TAC (2.88±0.56mmolTxEq/L), TOS(8.27±1.57μmolH2O2Eq/L), and KIM-1(0.55±0.08ng/mL) before SWL were not significantly different from mean TAC,TOS and KIM-1 levels measured from the control group at 2.81±0.42mmolTxEq/L, 10.73±1.4μmolH2O2Eq/L and 0.51±0.07ng/mL, respectively. Two hours after SWL, mean urine TAC levels (2.81±0.85mmolTxEq/L, p=0.02) were decreased and mean KIM-1 expression (0.85±0.11ng/mL, p=0.01) was significantly increased, but there was no significant difference in mean TOS levels (11.24±1.9μmolH2O2Eq/L, p=0.627) as compared to the control group.

CONCLUSIONS: The increased burden of free radical oxidants in the setting of decreasing antioxidant capacity may be one of the initial indicators of AKI following SWL. Moreover, KIM-1 demonstrates great potential as an early and noninvasive biomarker of SWL induced kidney injury.

Kommentare
1

Like several other similar studies in search for acute injurious effects of SWL, this report presents data on discrete changes in production of markers of free radical oxidants. The unique feature of this report was the use of kidney injury molecule-1 (KIM-1). No long-term follow-up was carried out in the present study and it is thus not known how fast the tissue would recover from the negative effect of free radicals.

Analysis of KIM-1 might be a useful tool for evaluation of effects associated with radical changes of SWL technology or treatment regimens, but there is no clinical need of such measurement in the way SWL presently is carried out. Morphological and transient effects of SWL are well recognized since more than 25 years.

Like several other similar studies in search for acute injurious effects of SWL, this report presents data on discrete changes in production of markers of free radical oxidants. The unique feature of this report was the use of kidney injury molecule-1 (KIM-1). No long-term follow-up was carried out in the present study and it is thus not known how fast the tissue would recover from the negative effect of free radicals.
Analysis of KIM-1 might be a useful tool for evaluation of effects associated with radical changes of SWL technology or treatment regimens, but there is no clinical need of such measurement in the way SWL presently is carried out. Morphological and transient effects of SWL are well recognized since more than 25 years.
Hans-Göran Tiselius